Vehicles, especially four wheel drive and off-road vehicles, may be equipped with a vehicle suspension system which includes a stabilizer bar or stabilizer bars (one for the front and one for the rear). Generally, a stabilizer bar includes a torsion bar that links two wheels together so they act in unison at high speed. For example, the stabilizer bar enhances drivability on smooth road surfaces by resisting instability as a vehicle changes lanes. On the other hand, the same high rigidity imparted by the stabilizer bar may degrade traction and independent wheel articulation on rough off-road surfaces. In addition, the high rigidity of the stabilizer bar may cause the traction of the left side and right side wheels to differ significantly causing differential transmission of driving torque which may further degrade road handling characteristics on rough road surfaces. Therefore, a stabilizer bar disconnect system driven by an actuator may be used to deactivate the stabilizer bar when driving on rough road conditions.
However, if failures such as external actuator electrical or internal actuator electrical failures occur, the actuator may become stuck in an “off-road” position with the stabilizer bar deactivated. This “off-road” position is undesirable for most smooth road driving conditions. Hence, reduced drivability could lead to a greater likelihood of accidents such as rollovers on smooth road conditions until the failure problem is repaired.
Accordingly, there is a need for an actuator with a failsafe mechanism for controlling an actuator driven element, particularly a stabilizer bar mechanism in a vehicle, which permits return of the actuator driven element to a more safe default position in case of a failure condition such as an external or internal electrical failure.